382 Miscellaneous Intelligence. 



the consistence of syrup, and suffered to remain for a month ; 

 when beautiful octoedral crystals, of a wine-yellow colour, were 

 formed on the sides of the vessel. On examination, it was 

 found to contain ammonia, and to be an alum, in which per- 

 oxide of iron supplied the place of alumina. 



The salt dissolves in three parts of water at 60°, and, by re- 

 peated crystalUzation, may be obtained, perfectly colourless. 

 On careful analysis, 100 parts appeared to be composed of 

 Per-sulphate of iron . . 41.807 

 Sulphate of ammonia . 12.366 

 Sulphate of alumina . . 0.870 



Water 



On further examination. Dr. Forchhammer found the sulphate 

 of alumina to be accidental, and neglecting it, ascertained the 

 composition to be, 



Per-sulphate of iron . . 41.95 

 Sulphate of ammonia . . 12.11 



Water 45.94 



He considers it as identical with the salt formerly described by 

 INIr. Cooper, as a bi-persulphate of iron. 



As the results deducible from this analysis seemed to agree 

 so well with M. Mitscherlich's idea, that per-oxide of iron and 

 alumina are isomorphous, and afforded additional proof of the 

 correctness of his views, Dr. Forchhammer was more earnest 

 to ascertain the exact quantity of water, and to compare it with 

 ammonia alum ; which salt gave, on analysis. 



Sulphuric acid .... 35.90 

 Alumina ..'... 11.50 



Ammonia 3.86 



Water and loss .... 48.74 

 This alum is, therefore, composed of three atoms of sulphate 

 of alumina, one atom of sulphate of ammonia, and 24 atoms of 

 water — and the triple salt above described, of three atoms of 

 per-sulphate of iron, one atom of sulphate of ammonia, and 

 24 atoms of water. — Ann. Phil. v. 



12. Test for Proto-salts of Iron. — Professor Ficinus, of Dres- 

 den, strongly recommends a solution of muriate of gold, as the 

 most delicate of all tests for the presence of protoxide of iron 

 in solution, surpassing considerably even the gall nut. It re- 

 quires the presence of carbonate of soda, which, in some ana- 

 lyses, may perhaps interfere with its use. A grain of green 

 vitriol, with an equal weight of soda, dissolved in four pints of 

 water, produces, with a drop of solution of muriate of gold, a 

 strong precipitate, which gradually assumes a purple colour. 

 Without the soda, the effect did not appear in less than three 



